Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare it is a non-read-only, non-destructive mutation, so the safety profile is covered structurally. The description adds a genuinely useful auth requirement (scope 'billing:authorize') that annotations do not carry. It says nothing about irreversibility of the budget grant, the 24h idempotency behavior exposed by the schema, or what happens on partial failure.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Three short sentences, zero filler, with the scoping constraint front-loaded before the alternative and the auth requirement last. Every sentence carries distinct routing or precondition information.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a 10-parameter financial-authorization mutation with no output schema, the description covers the two things an agent most needs before calling: whether this is the right tool and what scope is required. The remaining gaps (what the authorization grants, terms acceptance obligations, budget caps) are largely documented in the schema's 70% coverage.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

With 10 parameters and 70% schema description coverage, the schema does the heavy lifting and the description adds no parameter-level meaning at all. It does not mention budget_cents, accept_terms, failure_remedy, rails/offers, or the idempotency_key. Baseline 3 is the right ceiling given coverage, but nothing pushes it higher.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description never states the action in verb+resource form; it only frames the tool as 'Legacy frontier-offer budgets only.' The tool name and title carry most of the meaning, and the description's contribution is a scope/legacy qualifier plus a routing pointer. It does differentiate from the sibling authorize_credit_spending, which lifts it above a bare tautology.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicitly states when to use it ('Legacy frontier-offer budgets only'), when not to ('For current model services'), and names the alternative (authorize_credit_spending). It also names the required scope 'billing:authorize', so an agent knows a precondition before calling.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.